Steering mechanism



F. J. ADAMS STEERING MECHANISM Dec. 13, 1960 2 Sheets-Sheet 1 Filed June 19, 1958 F. J. ADAMS STEERING MECHANISM Dec. 13, 1960 2 Sheets-Sheet 2 Filed June 19, 1958 Q Q VW. .s m m w ik|1| F 4 l I l l Il |l 1 7 I 4 L x MN mm 6 mm V N 7 f 7 d\ n 7 Q Fw m WN @N @N QN N NM. N ,o\u

United States Patent STEERING lVIECHANISM Frederick John Adams, Houghton Regis, near Dunstable',

i lnglland, assignor to Hydrosteer Limited, Luton, Eng- Filed June 19, 1958, Ser. No. 743,053

Claims priority, application Great Britain Jan. 21, 1958 6 Claims. (Cl. 121-41) This invention relates to steering mechanism intended mainly for use on road vehicles: the invention more particularly is concerned with such mechanism as is commonly known as the power-assisted type in which the manual steering action is applied through a limited lost motion to a power control valve which regulates the injection of power into the transmission.

The main object of this invention is to provide a compact form of control valve assembly which shall be simple and relatively cheap to manufacture and to maintain.

According to the present invention a control valve comprises a valve housing having connections to a fluid pressure supply, to a fluid return and to the respectively opposite sides of a double acting fluid-pressure motor coupled to the steering transmission: in addition, a valve body is movable in the housing and cooperates through improved means and in a novel manner with the housing to provide in parallel with one another, flow paths between the supply and return connections and, in each flow path, a flow restriction and a normally open flow closure' to return which closes when the corresponding restriction is decreased.

The connections to the opposite sides of the power unit are taken respectively from the parallel flow paths at a point between the restrictions and the closuresthus in the neutral position of the valve body, flow occurs equally in both parallel paths (i.e. via the flow restriction and the closure in each path) between the supply and return connections: equal pressure reactions are therefore set up by the parallel restrictions and hence on the two sides of the motor: when however the valve is displaced from the neutral position, the flow to one path is increased at the same time that that path is closed to return: the flow to the other path although open to return is restricted increasingly as the valve body is displaced. In the result therefore an increasing proportion of the fluid is diverted to one side of the motor and a reducing proportion is diverted to the other side so producing the required operation of the power unit and hence of power injection.

In a preferred arrangement the valve body is in the form of a hollow cylindrical bobbin structure the periphery and the end walls of which cooperate with the circumferential and end walls of a hollow cylindrical housing to provide the parallel flow paths: the housing has a pressure liquid supply connection in its circumferential wall i.e. between the parallel flow paths. The periphery of the bobbin has flank surfaces cooperating with flank surfaces on the housing to provide the flow restrictions: the end walls of the bobbin and the housing are fitted with the flow closures and the housing is formed between the restrictions and the closures with branch connections extending to opposite sides of the power unit.

It is advantageous to constitute the closures by resilient rings which are carried either by the valve housing or by the valve body and are disposed between them so that when the body is moved axially in one direction or the other, one of the rings is compressed to provide P CE the closure to return at the same time that the corresponding flow resistance is reduced.

The invention is illustrated in the accompanying drawings in which Figure l is a sectional elevation of one form of control valve in accordance with the invention and Figure 2 shows that valve incorporated in a powerassisted steering mechanism of the screw and nut type.

Referring to the drawings the control valve is applied to a manually operated steering column 1 which is arranged to be displaced axially a small amount under the reaction of the steering gear proper.

The movable valve element or body is in the form of a hollow cylindrical bobbin 2 which is disposed concentrically about the column 1 and is connected to it by airing of balls 3 accommodated in a recess in the body 2 and in a peripheral recess 4 in the column: thus while the column can turn in the bobbin valve, the two are held against relative axial movement.

The valve body is disposed in a cylindrical chamber 5 in a valve housing 6 in which the column is mounted totturn and to move axially between the spaced rigid housing end walls: a pressure liquid supply connection indicated at 7 opens to a passage 8 in a circular or annular flangeportion 9 fast in the housing and entering the chamber 5: this flange 9 is disposed between rigid end flanges 10, 11 on the hollow bobbin 2, the various flanges providing surfaces radially overlapping opposite sides of the annular portion 9 and thus providing flow restriction passages 18, 19 which are of annular form. The rigid sides or end faces 12, 13 of the bobbin define between themselves and the adjacent end walls 14, 15 of the chamber 5 annular clearance spaces 16, 17' which serve as by-pass passages, being connected to the supply passage 8 via the restricted flow paths 18', 19 and to a return connection passage provided by an annular clearance 20 between the bobbin 2 and the column 1, the clearance opening via a port 20 to a return passage 21 in the column.

The hollow bobbin 2 is biased to its neutral (central) position by Belleville washers 22 which are carried by the end walls of the chamber 5 in the housing and bear against the sides of the bobbin. The end walls of the chamber are also fitted each with an 0 closure ring 23, the rings being disposed in the flow paths afforded by the clearances 16, 17.

The housing is also formed with passages 24, 25 which open to the passages 16, 17 between their connections to therestrictions 18, 19 and their closures 23 and these passages 24, 25 are arranged to be connected to the re spectively opposite sides of the fluid motor.

When therefore the bobbin 2 is in its central position pressure liquid can flow from the supply 8 via the pressure restrictions 19, 18 equally to both flow paths 16, 17 and thence past the rings 23 to the return 20', 20, 21 building up equal pressures in the passages 24, 25 and hence on the opposite sides of the motor.

When however the bobbin 2 is moved away from its central position, one or other of the flow restrictions 18 or 19 is decreased and the other is varied inversely, i.e. increased: at the same time the closure 23 in the flow passage 16 or 17 which receives liquid through the restriction which is decreased is engaged to close that passage to return. As a result, the flow of pressure liquid which normally passes equally via the two parallel flow paths 16, 17 is varied by increasing the flow to one parallel path at the same time that the path is closed to return: the flow to the other parallel path is reduced by the increased flow restriction set up by the corresponding restriction 18, or 19, but such flow as does occur can pass to return via i.e. past the ring 23. Since the rigid housing end walls and the rigid sides 12, 13 of the valve element 2 extend radially both inwardly and out- Wardly beyond the sealing rings 23, the latter are directly 7 compressible by relative approaching movement of the rigid housing walls and rigid valve element sides, no bending stresses being set up in the rings 23.

The motor is therefore operated to inject power assistance into the steering action. It will be clear that -the pressure which is applied to the opposite sides of the motor will react against the corresponding end wall of the bobbin 2 so tending to re-set it to its neutral position: this re-setting force is transmitted via the balls 3 to the column 1 and gives a sense of road-feel to the driver as the force acting on the column axially is proportional to the pressure acting on the motor and hence on the mechanism. The force is also proportional to the area of the annulus between the O ring 23 and the outer diameter of the bobbin 2 and thus the arrangement enables different sense of feel to be easily provided by choice of the diameter of the rings.

Referring to Figure 2, the housing 6 for the bobbin valve 2 forms an end wall of a cylinder 26 in which is. mounted a power ram 27. The passage 24 in the housing 6 opens direct to the cylinder 26 at one side of the ram 27 and the other passage 25 opens to a clearance 28 between the cyhnder 26 and an enclosing jacket 29 whence pressure liquid passes into the cylinder at the other side of the ram via ports 30.

The column 1 in that arrangement is fast with the screw 31 of a screw and nut gear of which the nut 33 has an extension or connection 32 to the ram 27 which itself slides on the steering column 1 which is itself permitted limited axial movement under the reaction between the screw 31 and the nut 33: as shown the screw and the nut cooperate through balls 34 which are free to circulate in a closed path including the helical track defined by the threads on the screw and the nut. The limited axial movement of the steering column 1 referred to above is possible because of the mounting of the left (as viewed in Figure 2) end of the column in roller bearings and the mounting of the right end of the column in the bobbin 2, which itself is slidable in the housing 6. When the column is turned manually, the balls 34 react against threads of the screw 31 and thus produce an axial reaction thrust on the column 1. This moves the column 1 axially, and, through the balls 3, moves the bobbin structure 2. The movement of the bobbin structure 2 gives rise to the valve control which causes the ram 27 and hence the nut 33, rocker arm 35, rocker shaft 36 and drop arm 37 to be operated.

In the arrangement shown, the steering wheel would be mounted at the right hand end of the column 1 and the nut 33 would be connected as is usual to a rocker arm indicated at 35 on a rocker shaft 36 -having a drop arm 37 connected to the steering transmission.

It will be appreciated that a valve according to the present invention can be incorporated in any of the various known types of power-assisted steering gear. In Fig. 2 it is shown applied to a mechanism of the screw and nut type which incorporates also the invention claimed in the copending application of Frederick John Adams, Serial No. 752,250, filed July 31, 1958, now abandoned, in which the power unit is fitted as 'a unit inline with the screw and is coupled to the nut.

I claim:

1. In a steering gear power control valve, a housing providing a chamber having an axis, axially spaced rigid end walls and an annular portion projecting into said chamber between and spaced from said end walls; a valve element having rigid sides and being mounted for axial movement within said chamber between said end walls; restrictive flow regulating surfaces in the form of rigid flanges on said valve element radially overlapping opposite sides of said annular portion and, in combination with said opposite sides, providing two restricted flow paths which are relatively inversely variable in flow restricting size according to the direction of movement of said valve element in said chamber; a pressure fluid supply connection communicating with said restricted flow paths; two separate pressure fluid delivery passages in said housing respectively communicating with said restricted flow paths, said .restricted fiow paths intervening between said pressure iluid supply connection and said pressure fluid delivery passages; two by-pass passages between rigid opposite sides of said valve element and the rigid end walls of said housing respectively adjacent thereto and communicating with said pressure fluid delivery passages; a return passage communicating with said by-pass passages; resilient sealing rings respectively in said by-pass passages between each of said valve element opposite rigid sides and the rigid end wall of said housing adjacent thereto and intervening between said pressure fluid delivery passages and said return passage, said housing rigid end walls and said valve element rigid sides extending radially both inwardly beyond and outwardly beyond said sealing rings whereby said rings are respectively directly compressible by relative approaching movement of the associated valve element rigid sides and housing rigid end walls; and means for moving said valve element axially in said chamber.

2. Steering gear power control valve according to claim 1 including two Belleville washers interposed respectively between opposite sides of said movable valve element and the adjacent opposite end walls of said housing.

3. Steering gear power control valve according to claim 1 in which the means for moving said valve element axially in said housing is formed as the steering column of a power assisted steering gear, said steering column extending axially within and being surrounded by said valve element.

4. Steering gear power'control valve according to claim 1 in which said movable valve element is a bobbin having spaced flanges the opposed faces of which constitute the restrictive flow regulating surfaces radially overlapping the opposite sides of the said annular portion.

5. Steering gear power control valve according to-claim l in which the means for moving said valve element axially in said housing comprises a column mounted for rotary and axial movement in said housing; and means connecting said column to said valve element for rotation relative thereto and restraining said column and said valve element from axial movement relative to each other.

"6. Steering gear power control valve according to claim 5 in which said column extends axially through said valve element and in which said column and said valve element are formed with concentric recesses, .said construction including a ring of balls accommodated in said recesses.

References Cited in thefile of this patent UNITED STATES PATENTS 2,634,708 Davis Apr. 14, 1953 2,739,613 Kulikoff Mar. 27, 1956 2,815,737 Gold Dec. 10, 1957 2,860,605 Banker Nov. 18, 1958 2,875,781 Hruska Mar. 3, 1959 2,932,283 Jefiery Apr. 12, 1960 

